In recent years, there is a special structure material. With its unique structure and rich physical characteristics, it has become the focus of quantum material research-it is a cage Materials.
Written article | Luo Huiyue (Institute of Physics of the Chinese Academy of Sciences)
In recent years, there are a special structure of a special structure in recent years. Materials- "cage materials" have become the pets of condensed state physicists.People have found a variety of wealth of material such as iron magnetic, superconducting, topology, charge density waves, etc. in this kind of materials, and they also present a series of very significant quantum transportation characteristics, indicating huge application potential Essence
What is the cage structure?What are the characteristics of the materials constructed by the cage structure unit?What are the important research value as an emerging quantum material?Now, lets talk about the magical and changeable cage structure materials.
The structure of the cage eyes is actually very common in our lives.If you go to the south, you will find many weaving bamboo cages, bamboo baskets, and bamboo baskets. Their holes are all hexagonal, surrounded by six equivalent triangles, that is, the "hexagonal stars that shared the top point one by one "composition.Similar fabrics are also very common in Japan. There is a nursery rhyme in Japan called "cage eyes". English is Kagome Kagome, where Kago is a basket, and Me means eye. Citic translation is "eye -catching basket". Essence
Bamboo cages, bamboo baskets, bamboo baskets, bamboo baskets
In 1951, the Japanese scientist iTiro Syoz proposed the concept of cage structure material, which refers to the micro -atomic lattice that can also constitute the six -pointed star array of the vertex, that is, Kagome Lattice, that is, "cage lattice".It can be seen that, like the positive triangle, positive quadrilateral and positive hexagonal, the cage structure unit is also a way to densely flatter the two -dimensional plane, and at the same time takes into account the characteristics of hexagonal and triangles.Why is the cage structure material so special?If we carefully observe the cage lattice, we will find that each atom of them needs to be combined with the four surrounding atoms, and the four chemical bonds are distributed on the shape of the top triangle.Assuming that the atomic chemical price is between three or four -valent, then one of the chemical bonds may not be stable, and strange things happen at this time.For example, the top angle in a certain direction will be distorted, so that the overall structure of the material will have certain distortion, which will also change the charge distribution and form a charge density wave of the cycle distribution.If the electrons turn left around or turn right, it will be found that there are differences between the two, which means that the material structure or electronic state is handicap.
Two-dimensional cage structure
Similar The ancient pane of the cage structure
What is more interesting is that if the atom is added with a magnetic moment, which means that they are like CO, Mn, Fe, Cu, and rare earth ions like Magnetic atoms, then you will find that this small magnetic needle is very rich in the placement of each vertex of the triangle.The simplest is that the magnetic torque is completely consistent and perpendicular to the two -dimensional cage plane, which is an iron magnet.If the magnetic torque is placed in the plane of the cage, the thing becomes not so simple. The three magnetic combinations can be a 120 -degree angle of each other, so that it can exist steadily, but it is troublesome to be slightly deviated.Because for the two atomic magnetic torque combinations, they tend to either arranged in the same direction or reversely arranged; but for the three magnetic combinations of a triangle, if two or two are required, it will be found that it is almost impossible to find that it is almost impossible To do, that is, A and B are opposite, B and C are opposite, then A and C are bound to be the same.This phenomenon is called geometric blocking in material science, which means that there is always a state of a certain atom "uncomfortable", which causes the nature of the material to change many.
Copper Cage Structure Dirac quantum magnet
The frustration effect of "restlessness" also appears a series of strange properties in its micro -electronic state.Simply put, in terms of electrons, we can observe that we can observe the Dirac spots such as the four briefs, the colorless flat band, and the Vanhofz.These nouns sound very mouthful, probably meaning that the energy-momentum distribution of electrons will show relatively abnormal behavior. For example, the energy-momentum relationship is simple linear cross, almost no state of dynamic dependence, and the distribution status of the saddle shape.It is precisely because of the existence of these very interesting micro -electronic states that it means that the cage materials will also present a series of special behaviors in the macro state. We collectively referred to as an abnormal quantum transportation behavior.For example, quantum abnormal Hall effect, topological Hory effect, quantum spin liquid, huge magnetic resistance effect, huge energy effect, and so on.These effects laid the foundation for further constructing a new type of quantum device.In optical research, the concept of cage lattice can also be used to construct the eye crystal and make a beam of laser become the shape of the cage after passing through, which is also very interesting.
Various complex charge sequences of cage structure pattern
photon crystals of cage structure
Cage structure materials show a variety of state at low temperature.For example, the iron magnets mentioned earlier are relatively common, as well as superconductors, charge density waves, spin -density waves and other states.And because the structure of the cage is a quasi-two-dimensional structure, if different cage planes are stacked together, the orderly-disorderly change of stacking can also appear, and it can even be artificially designed to build a new material.
Materials that have a cage structure and have a strong self -spin, and are considered an important candidate for quantum spin liquid.In recent years, a number of materials with cage structure have been found in CU, RU, CO and other compounds. The magnetic atomic interaction in them is very strong, but it is often difficult to form a stable magnetic order structure at low temperature. Therefore The spin is always moving because the quantum rises and falls, just like the liquid properties, this state is called the quantum spin liquid.
In the future, if you can find a richer material state in cage materials and regulate it, it may also achieve low energy consumption and high -stable topological quantum calculations.As the day of group pets, cage materials have just begun!
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